Sunday, May 1, 2016

Why Is That S-Curve There?

While playing with Google Maps,
he noticed that much of the Midwest is made up of colorful squares
outlined by straight roads that are broken up every 24 miles or so by a
sharp jog to the left or right. Ruijter found them so fascinating that
he made them the subject of a photo series, Grid Corrections.
These kinks in the road date to the earliest days of the US. After
the American Revolution, the bureaucrats of the Surveyor General’s
office faced the daunting task of parceling out vast swaths of land
they’d never seen. To open western territories like Kansas to
settlement, surveyors divided land into 160-acre plots—plenty of room
for a family to settle and farm comfortably, says Steven Schrock, a
civil engineer with the University of Kansas.
It being the Age of Enlightenment and all, the surveyors relied upon
orderly and logical straight lines that intersect at 90-degree angles,
forming the grid that the Midwest is known for.
There’s one problem with that: The world is not flat. Its oblate
spheroid shape has long vexed cartographers, who must often distort
reality to make it fit into a functional, two-dimensional survey. But
those little fudges catch up with you when you build roads based on
those maps. “If you put enough squares on a (more or less) spherical
Earth, eventually you have to offset the boundaries so that you end up
with what [de Ruijter] is calling ‘grid corrections’,” Schrock says.
Uncorrected, this problem does things like make Greenland the same size as Africa on a Mercator map.
Those early American surveyors wanted to make each plot the same size
IRL, so they inserted border corrections. When communities laid roads
along the borders of these plots, they made those small kinks a little
larger so horse-drawn wagons could navigate them more easily. The
arrival of the automobile required making them larger still, because
cars are faster than horses.

That stuff is even more complicated than it sounds. I've posted on the rectangular grid system a few times in the past, and that's because it fascinates me and shapes the world I live in.